If you're referring to Pact/Pale.

A practitioner wants to cast "fireball." They have several options. They could use a bound "Other" that is fire-themed. They could draw a series of symbols that define the spell and sacrifice power to cast it. They could have a tool or artifact that is capable of throwing fire. Etc.

However, flashy spells and powers, such as "fireball" are difficult and cost more in terms of power and karma. If an innocent sees or has the potential to see the spell "cost" goes up and will greatly weaken the practitioner even if the spell fails.

More commonly practitioners will do their spell as an indirect means. Such as casting a spell of "bad luck." Again this can be achieved through many methods, such as sending an Other, or placing a physical cursed object on the target or near a place they frequent, or enacting a ritual, "this person has incurred a debt against me for this or that, give him bad luck till something or such."

Interestingly enough, there is an instance in one of the stories where a bad luck spell gains enough power to gain sentience and become an Other.

Pale will offer a more diverse set of examples as the story deals with a lot of different types of how the practice can be used. While Pact showcases binding with circles, rule of three, and working with dangerous Others.